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6 Atomic Chains, Clusters, and Nanocrystals
6.4 Silver
6.4.1 STM/S-DFT: Adatom Polarization
STM/S profiles in Fig. 6.4a show the polarization (bias positive) of Ag atoms added
onto Ag(111) surface [46, 47]. The extent of polarization increases with the reduction
of cluster size. The shell-resolved LDOS and the size-resolved DOS in Fig. 6.4b,
c follow the same trend of BOLS-NEP prediction of polarization. The outermost
shell of a cluster and the smallest dot polarize the valence electrons most [11]. The
size-enhanced polarization explains why Ag participles could enhance the Raman
signal or plasmonics with respect to their bulk parent [48] and why the size and
shape influence its biocide property [49] from the perspective of core electron local
quantum entrapment and valence charge polarization.
6.4.2 APECS: 3d and 5s Band Cooperative Shift
Figure 6.5 shows the Ag 3d core level shift as a function of thickness. The STM image
shows the patterns of the Ag clusters on CeO 2 surface [50]. The APECS profiles, i.e.,
(a) XPS core level shift, (b) valence band, and (c) Auger parameter, in Fig. 6.6, for
Ag particles deposited on CeO 2 surface [50–53] are the same to that of Ag clusters
on Al 2 O 3 surface [54–57]. Results show consistently that the E 3d5/2 increases and
the Auger parameter (E 3d + E K ) drops in magnitude when the crystal size is reduced.
Ag particle size reduction polarizes the valence charge slightly. The 3d states of Ag
particles on HOPG [58] and on TiO 2 [59] follow the same size trend of core level
Fig. 6.5 a XPS spectra and b STM image of Ag clusters deposited on CeO 2 surface. Reprinted
with permission from [50]. Copyright 2011 American Chemical Society
6 Atomic Chains, Clusters, and Nanocrystals
6.4 Silver
6.4.1 STM/S-DFT: Adatom Polarization
STM/S profiles in Fig. 6.4a show the polarization (bias positive) of Ag atoms added
onto Ag(111) surface [46, 47]. The extent of polarization increases with the reduction
of cluster size. The shell-resolved LDOS and the size-resolved DOS in Fig. 6.4b,
c follow the same trend of BOLS-NEP prediction of polarization. The outermost
shell of a cluster and the smallest dot polarize the valence electrons most [11]. The
size-enhanced polarization explains why Ag participles could enhance the Raman
signal or plasmonics with respect to their bulk parent [48] and why the size and
shape influence its biocide property [49] from the perspective of core electron local
quantum entrapment and valence charge polarization.
6.4.2 APECS: 3d and 5s Band Cooperative Shift
Figure 6.5 shows the Ag 3d core level shift as a function of thickness. The STM image
shows the patterns of the Ag clusters on CeO 2 surface [50]. The APECS profiles, i.e.,
(a) XPS core level shift, (b) valence band, and (c) Auger parameter, in Fig. 6.6, for
Ag particles deposited on CeO 2 surface [50–53] are the same to that of Ag clusters
on Al 2 O 3 surface [54–57]. Results show consistently that the E 3d5/2 increases and
the Auger parameter (E 3d + E K ) drops in magnitude when the crystal size is reduced.
Ag particle size reduction polarizes the valence charge slightly. The 3d states of Ag
particles on HOPG [58] and on TiO 2 [59] follow the same size trend of core level
Fig. 6.5 a XPS spectra and b STM image of Ag clusters deposited on CeO 2 surface. Reprinted
with permission from [50]. Copyright 2011 American Chemical Society